The ghosts can also sing, or shout, or whisper, or make noise, etc ..., but in this case it is not the soul of your grandmother, since the souls of the dead are in astral, or place that God has pre-established for all the souls of the dead, until the day of his judgment!
Therefore, God's permission has not been given that souls come to earth to visit their close relatives, and we do not communicate with them, this was God's plan in his word!
Therefore, any noise, or other, is to be considered presences of demons that with their faculty have the power to do what the dead were doing before dying, this because the spirits are deceptive, they can also appear with human features, and with the same physiognomy of the deceased relatives.
Unfortunately, it is difficult for people who have had such experiences believe what I have said.
So if what you've really happened, this is the truth!